Life cycle GHG emissions of reformulated gasoline (containing
2.3% oxygen by weight), derived from GREET [22], are the reference
for comparison with those of ethanol, taking into account the positive
consequence of ethanol blending with gasoline in terms of octane
rating improvement. Oxygenates other than ethanol like
methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and
tert-amyl methyl ether (TAME) have been used to boost octane levels
in unleaded gasoline and/or to meet clean fuel oxygen requirements.
For ethanol in E10 and E20 blends, we adopt an equivalence
of 1 L ethanol (anhydrous) = 0.8 L gasoline which was derived by
Macedo et al. for E25 [6]. This ratio would be reasonable for E20
but slightly low for E10 compared to the 0.89 ratio used by Nguyen
et al. [12]. It is worth noting that Macedo et al. derived this equivalence
based on the relative performance of new vehicles.